This application claims priority from United Kingdom Serial No. 9825118.4, filed Nov. 16, 1998. This invention relates to a breath-actuated dispenser for administration of a product in the form of aerosolised solid particles or droplets of liquid or suspension or gas. In particular, the invention relates to such devices which are actuated to dispense medicament to a patient in response to the patient""s inspiration.
It is well known to treat respiratory diseases such as asthma by the inhalation of appropriate medicaments in the form of an aerosol. Conventionally these inhalers use pressurised containers to dispense the medicament in the form of an aerosol through a valve in the container. Various types of valve are known. Firstly, a xe2x80x9cpress to firexe2x80x9d valve in which a valve stem is pressed to open the valve. Secondly, a xe2x80x9crelease to firexe2x80x9d valve in which a valve stem is pressed to prime the valve and when the force on the valve stem is released the valve moves to an open position to release the medicament. Other types of valve include a xe2x80x9cpull to firexe2x80x9d in which the valve stem is moved outwardly to the firing position and xe2x80x9crelease to fire on inward strokexe2x80x9d in which the valve stem is held against an inward bias until released to move inwardly and fire. Generally, the valves used are of the xe2x80x9cmetered dosexe2x80x9d type in which when the valve opens only a predetermined, metered dose of the medicament is released from the container.
These known devices are generally manually operated and require a user to manually trigger the inhaler while breathing in. Such devices can be difficult to ensure proper usage since they require coordination often when a patient may be in distress.
Breath-actuated dispensers in which the act of a user breathing in triggers the valve to release the medicament from the container have been proposed in numerous patents. In practice there are few types of breath-actuated dispensers commercially available since it is a complex task to mass produce devices which are capable of meeting the precise requirements of breath-actuator throughout the life of the medicinal aerosol product.
U.S. Pat. No. 3,814,297 discloses a breath-actuated dispenser comprising an aerosol container having a metered dose dispensing valve which is primed by depression and discharges through the stem when the stem is released, a duct having an inlet and outlet, means to receive the aerosol container with the valve stem communicating with the duct, a strut engageable with the stem and manually operable to press the stem inwardly to its priming position, a vane pivotally mounted in the duct movable in response to air flow in the duct and a lever arm attached to the strut and engaged by the pivot whereby when the valve is primed the stem is prevented from moving to its firing position by the strut and when a patent inhales through the outlet the vane pivots causing movement of the lever and strut to release the stem allowing the valve to fire.
GB-2292891 discloses an actuator for a breath-actuated medicament dispenser comprising a cap which is manually depressed to apply a priming/firing force to the dispenser and a restraining means to prevent the device firing until patient inhalation. The restraining means may comprise a piston movable in response to inhalation and a latching device comprising a pivotally mounted latch member whose movement is blocked in the primed position by a ball positioned between the latch member and piston. Movement of the piston in response to inhalation causes the ball to disengage the latch member allowing firing of the device.
The present invention provides an alternative construction of breath-actuated dispenser. According to the present invention there is provided a dispenser for dispensing a product from a pressurised product container comprising a housing defining a user port and adapted to have a pressurised product container mounted therein, the pressurised product container having a dispensing valve movable relative to the container between an open and a closed position; the housing further comprising a rolling member comprising a vane, and an associated rolling surface, the rolling member being capable of rotation involving relative translational movement along the rolling surface in response to inhalation through the user port between a locking position in which the rolling member is engaged between the rolling surface and the pressurised product container or valve to maintain the valve in the closed position, and a release position in which the valve and the pressurised product container move relative to each other so that the valve moves to the open position to dispense product from the container and towards the user port.
An advantage of the invention is that by providing a rolling member and an associated rolling surface it is possible to provide a breath-actuated dispenser in which the triggering force is reduced compared with the prior art. This is particularly useful when treating patients having respiratory diseases such as asthma. In a situation where the patient requires the inhalation of a medicament, he or she may be unable to inhale strongly and therefore easy triggering of the inhaler is highly advantageous. In addition, it is also possible to provide a breath-actuated dispenser of a relatively simple construction.
In one embodiment the housing comprises a biasing device to apply pressure between the rolling member and the container.
The rolling member comprises a vane which moves in response to air flow generated by inspiration through the user port to cause the rolling member to rotate and translate from the first position to the second position. The vane presents a large surface area to the airflow generated by user inspiration thereby lowering the rate of inhalation required to trigger the device.
In a further embodiment, the pressurised product container is pivotally mounted within the housing and the rolling surface is stationary within the housing. In another embodiment the container is fixed relative to the housing and the rolling surface is pivotally mounted.
It is also preferred that a resetting mechanism be included in the device.